1. The Field of the Invention
The present invention is directed to methods and apparatus for monitoring blood constituents. More particularly, blood constituents such as glucose, are monitored noninvasively through diffusion across epithelial membranes.
2. Technology Review
The blood is routinely tested for various blood constituents in countless medical procedures. This typically involves drawing an actual blood sample from the patient, followed by blood analysis. Most people can tolerate giving an occasional blood sample, but continually drawing blood for analysis creates additional safety risks for the patient. For those persons suffering from diabetes mellitus (hereinafter referred to as "diabetes"), blood is often drawn many times a day.
Diabetes is a major health problem directly affecting over ten million people in the United States. The prevalence of the disease is increasing rapidly. Most people suffering from diabetes face the probability of major complications and shortened life spans. Diabetes is currently the seventh leading cause of death in the United States, and has been attributed to 35,000 to 50,000 deaths and costs of more than 20 billion dollars per year.
Diabetes is a disorder of carbohydrate metabolism characterized by elevated blood sugar (hyperglycemia), sugar in the urine (glycosuria), excessive urine production (polyuria), excessive thirst (polydipsia), and increase in food intake (polyphagia). Diabetes is a chronic, incurable disease, but symptoms can be ameliorated and life prolonged by proper therapy. Diabetes results from the inadequate production or utilization of insulin.
Insulin is a hormone secreted by the pancreas which is essential for the proper metabolism of blood sugar (glucose) and for the maintenance of the proper blood glucose level. Severe insulin deficiency, or less severe insulin deficiency coupled with other conditions, can cause ketoacidosis which may lead to coma and life-threatening crisis.
Chronic diabetes is associated with vascular and neurologic degeneration, and persons with diabetes are at increased risk of heart disease, blindness, renal failure, and inadequate circulation and sensation in peripheral tissues. Women with diabetes also have increased risk of stillbirths and congenital malformations in their children.
These direct consequences of diabetes make it a disease that is costly and difficult to manage. However, the complications of diabetes are caused primarily by elevated blood glucose levels, and these complications can be avoided in most cases by monitoring and control of blood glucose levels and close medical supervision with appropriate intervention. Thus, blood sugar determinations may need to be made at frequent intervals in order to know if, when, and how much insulin is needed to control blood glucose.
Attempts have been made to monitor blood glucose noninvasively. As used in this specification, the term "noninvasive blood glucose monitoring" means determining blood glucose concentration without actually drawing the patient's blood. For example, efforts to monitor blood glucose based upon glucose concentration in a patient's saliva or breath have failed. The reason for these failures is that there is no correlation between glucose in saliva or breath and the actual blood glucose levels. In fact, glucose does not naturally cross body membranes such as the buccal mucosa or membranes of the skin. Because most body membranes are naturally impermeable to glucose, the presence of glucose has historically been used to test whether tissue is intact in transdermal experiments.
In view of the foregoing, it will be appreciated that the development of apparatus and methods for noninvasive blood glucose monitoring would be a significant advancement in the art.
It would be another significant advancement in the art to provide apparatus and methods for noninvasive blood glucose monitoring which provide accurate and reproducible correlation with actual blood glucose levels.
Additionally, it would be a significant advancement in the art to provide apparatus and methods for noninvasive blood glucose monitoring which provide rapid results in sufficient time to administer appropriate medication.
Such apparatus and methods for noninvasive blood glucose monitoring are disclosed and claimed herein.